diff --git a/lib/SIL/IR/Linker.cpp b/lib/SIL/IR/Linker.cpp
index 6ff6c2bd8536f..c391114e05ee7 100644
--- a/lib/SIL/IR/Linker.cpp
+++ b/lib/SIL/IR/Linker.cpp
@@ -141,6 +141,20 @@ void SILLinkerVisitor::maybeAddFunctionToWorklist(
       // are also set to IsSerialized.
       Worklist.push_back(F);
     }
+
+    if (F->markedAsAlwaysEmitIntoClient()) {
+      // For @_alwaysEmitIntoClient functions, we need to lookup its
+      // differentiability witness and, if present, ask SILLoader to obtain its
+      // definition. Otherwise, a linker error would occur due to undefined
+      // reference to these symbols.
+      for (SILDifferentiabilityWitness *witness :
+           F->getModule().lookUpDifferentiabilityWitnessesForFunction(
+               F->getName())) {
+        F->getModule().getSILLoader()->lookupDifferentiabilityWitness(
+            witness->getKey());
+      }
+    }
+
     return;
   }
 
diff --git a/stdlib/public/Differentiation/SIMDDifferentiation.swift.gyb b/stdlib/public/Differentiation/SIMDDifferentiation.swift.gyb
index 904768cfd2588..e1da73241ab91 100644
--- a/stdlib/public/Differentiation/SIMDDifferentiation.swift.gyb
+++ b/stdlib/public/Differentiation/SIMDDifferentiation.swift.gyb
@@ -455,3 +455,27 @@ where
     return (Self(repeating: value), { v in Self(repeating: v) })
   }
 }
+
+%for (Scalar, bits) in [('Float',32), ('Double',64)]:
+% for n in vectorscalarCounts:
+extension SIMD${n} where Scalar == ${Scalar} {
+  @inlinable
+  @_alwaysEmitIntoClient
+  @derivative(of: init(repeating:))
+  static func _vjpInit(repeating value: Scalar)
+    -> (value: Self, pullback: (TangentVector) -> Scalar.TangentVector)
+  {
+    return (Self(repeating: value), { v in v.sum() })
+  }
+
+  @inlinable
+  @_alwaysEmitIntoClient
+  @derivative(of: init(repeating:))
+  static func _jvpInit(repeating value: Scalar)
+    -> (value: Self, differential: (Scalar.TangentVector) -> TangentVector)
+  {
+    return (Self(repeating: value), { v in Self(repeating: v) })
+  }
+}
+% end
+%end
diff --git a/stdlib/public/core/SIMDFloatConcreteOperations.swift.gyb b/stdlib/public/core/SIMDFloatConcreteOperations.swift.gyb
index 8c30a42b4fedf..71d2e91ba08ec 100644
--- a/stdlib/public/core/SIMDFloatConcreteOperations.swift.gyb
+++ b/stdlib/public/core/SIMDFloatConcreteOperations.swift.gyb
@@ -34,8 +34,6 @@ extension SIMD${n} where Scalar == ${Scalar} {
     _storage = ${Scalar}.SIMD${storageN}Storage(_builtin)
   }
   
-  /* Breaks differentiation testing, commented out while we figure out
-     what to do about that.
   @_alwaysEmitIntoClient @_transparent
   public init(repeating scalar: ${Scalar}) {
     let asVector = Builtin.insertelement_${Builtin}_FPIEEE${bits}_Int32(
@@ -52,7 +50,6 @@ extension SIMD${n} where Scalar == ${Scalar} {
     ))
 %end
   }
-  */
   
 %  if n >= 4:
   @_alwaysEmitIntoClient @_transparent
diff --git a/test/stdlib/SIMDFloatInitializers.swift.gyb b/test/stdlib/SIMDFloatInitializers.swift.gyb
index f728764d596d9..c535d57bf1de8 100644
--- a/test/stdlib/SIMDFloatInitializers.swift.gyb
+++ b/test/stdlib/SIMDFloatInitializers.swift.gyb
@@ -14,10 +14,6 @@
 // RUN: %target-swift-frontend -primary-file %t/SIMDFloatInitializers.swift -S | %FileCheck %t/SIMDFloatInitializers.swift --check-prefix=CHECK --check-prefix=CHECK-%target-cpu --check-prefix=CHECKOnone-%target-cpu
 // RUN: %target-swift-frontend -primary-file %t/SIMDFloatInitializers.swift -S -O | %FileCheck %t/SIMDFloatInitializers.swift --check-prefix=CHECK --check-prefix=CHECK-%target-cpu --check-prefix=CHECKO-%target-cpu
 
-// Disable this test for now because aEIC/transparent functions still are not
-// correctly differentiable, and so these inits are suppressed in the stdlib.
-// REQUIRES: differentiable-aEIC-transparent
-
 import Swift
 
 %for bits in [16,32,64]: